How to Lease IPv4 Addresses: A Step-by-Step Guide for Network Teams
From sizing the block to publishing the ROA — the seven steps that turn a lease agreement into announced, deliverable address space.
Leasing IPv4 space is not complicated, but it is unforgiving of shortcuts. A lease that skips the reputation check or the routing authorisation looks fine on paper and fails in production — mail bounces, prefixes get filtered, and you spend the first month of your contract firefighting. Here is the sequence that works.
1. Size the block honestly
Start from addresses actually needed, not addresses you might want. Count your public-facing endpoints, your NAT pools, your mail senders and a reasonable growth margin. Then round up to the nearest CIDR boundary: /24 (256), /23 (512), /22 (1,024) and so on. The /24 matters more than the arithmetic suggests. It is the smallest prefix most transit providers will accept in the global routing table, so anything smaller will only work inside a provider's own network. If you intend to announce the space yourself, /24 is your floor.
2. Decide between lease and purchase
At 2026 prices a transfer costs roughly **$27 per IP for a /24**, **$16 for a /20** and **$14 for a /19**. Leasing runs around **$0.40 per IP per month**. Under a two-year horizon, leasing almost always wins on cash; beyond that, purchase starts to look like the cheaper path — and leaves you holding an asset. The reference point worth keeping in mind is the cloud: roughly **$44 per address per year** for a public IPv4. Any lease materially below that is already saving you money against the default.
3. Find the space
There are three routes. **Brokers and leasing marketplaces** are the fastest and the most crowded; expect a commission and a standard contract. **Direct deals** with organisations sitting on unused blocks are slower but cheaper, because there is no intermediary — the hard part is finding them. **Your upstream provider** may lease you space directly, which is convenient but ties address space to connectivity, exactly the coupling most teams lease to avoid. The direct route is where market intelligence pays for itself. A block that is registered, dormant and clean is a lease candidate before it ever appears on a listing — and it is the one where you set the terms rather than accept them.
4. Verify reputation before you sign
This is the step people skip and regret. Ask for the prefix, then check it yourself: - Major blocklists (Spamhaus and equivalents) for current and historical listings. - Routing history — has the prefix been announced by unrelated ASNs, which can indicate a past hijack? - Whether the block was ever used for bulk mail or affiliate traffic. If your use case involves email, this check is the entire deal. Address space with a poisoned history is close to worthless for delivery, and cleaning it can take months.
5. Get the paperwork right
A lease should produce three artefacts: **The agreement** — term, rate, renewal cap, notice period, and an explicit reputation warranty with a remedy if the block turns out to be listed. **The LOA (Letter of Authorisation)** — the signed document that tells your transit providers you are permitted to announce this prefix. Without it, your upstreams will not accept the route. **Registry objects** — the holder updates the RIR records so the prefix reflects your operational use. In the RIPE region, which carries the highest transfer volume in the world, this is well-trodden procedure.
6. Publish RPKI and announce
Ask the holder to create an **RPKI ROA** authorising your ASN to originate the prefix. Networks increasingly drop RPKI-invalid routes, so a missing or wrong ROA means your traffic silently disappears for a growing share of the internet. Then announce the prefix to your upstreams and verify propagation from multiple looking glasses — not just your own router.
7. Monitor for the life of the lease
Reputation is not a one-time check. Watch for new blocklist entries, watch for anyone else announcing your prefix, and keep an eye on renewal dates — the worst time to discover your rate has doubled is the week your contract expires.
Where the leverage is
Everything above is executable. The part that is not evenly distributed is knowledge: which blocks exist, which are genuinely dormant, and which are clean enough to carry your traffic. That visibility is what separates a team negotiating from strength from one taking whatever the market offers. --- *See which blocks are quiet across all five RIRs on the IPDORM dark space map — [ipdorm.com](https://ipdorm.com).*